Dual stack compact fuel processor for producing a hydrogen rich gas

ABSTRACT

An apparatus for carrying out a multi-step process of converting hydrocarbon fuel to a substantially pure hydrogen gas feed includes a plurality of modules each module being in fluid communication with adjacent modules. The modules may be arranged axially along a common axis of flow or alternatively the modules are arranged along a common axis so that they are nested one within the other. The multi-step process includes: providing a fuel processor having a plurality of modules; and feeding the hydrocarbon fuel successively through each of the modules in the reactor to produce the hydrogen rich gas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/021,673, filed Dec. 12, 2001, pending, which claimed priority to U.S.Provisional Patent Application No. 60/255,027, filed Dec. 12, 2001 andU.S. Provisional Patent Application No. 60/261,232, filed Jan. 12, 2001.

BACKGROUND OF THE INVENTION

Fuel cells provide electricity from chemical oxidation-reductionreactions and possess significant advantages over other forms of powergeneration in terms of cleanliness and efficiency. Typically, fuel cellsemploy hydrogen as the fuel and oxygen as the oxidizing agent. The powergeneration is proportional to the consumption rate of the reactants.

A significant disadvantage which inhibits the wider use of fuel cells isthe lack of a widespread hydrogen infrastructure. Hydrogen has arelatively low volumetric energy density and is more difficult to storeand transport than the hydrocarbon fuels currently used in most powergeneration systems. One way to overcome this difficulty is the use ofreformers to convert the hydrocarbons to a hydrogen rich gas streamwhich can be used as a feed for fuel cells.

Hydrocarbon-based fuels, such as natural gas, LPG, gasoline, and diesel,require conversion processes to be used as fuel sources for most fuelcells. Current art uses multistep processes combining an initialconversion process with several clean-up processes. The initial processis most often steam reforming (SR), autothermal reforming (ATR),catalytic partial oxidation (CPOX), or non-catalytic partial oxidation(POX). The cleanup processes are usually comprised of a combination ofdesulfurization, high temperature water-gas shift, low temperaturewater-gas shift, selective CO oxidation, or selective CO methanation.Alternative processes include hydrogen selective membrane reactors andfilters.

Despite the above work, there remains a need for a simple unit forconverting a hydrocarbon fuel to a hydrogen rich gas stream for use inconjunction with a fuel cell.

SUMMARY OF THE INVENTION

The present invention is generally directed to an apparatus and methodfor converting hydrocarbon fuel into a hydrogen rich gas. One suchillustrative embodiment includes a reforming stack for converting thehydrocarbon fuel feed into a hydrogen rich gas; and a purification stackfor producing the hydrogen rich gas suitable for direct feed to a fuelcell. In one preferred illustrative embodiment, the reforming stackincludes a first plurality of cylindrical vessels, in which the firstplurality of cylindrical vessels are stackable without the need forconnecting piping between each vessel. Further, the purification stackincludes a second plurality of cylindrical vessels, in which theplurality of cylindrical vessels are stackable without the need forconnecting piping between each vessel. One illustrative embodiment hasthe reforming stack is aligned vertically. The reforming stack of oneillustrative embodiment includes a shift vessel, an autothermalreforming vessel, and an anode tail gas oxidation vessel. Thepurification stack of the illustrative embodiment includes an oxidationvessel, a first desulfurization vessel, and a second desulfurizationvessel. In the present illustrative embodiment, the hydrocarbon fuelfeed is sequentially introduced first, to the anode tail gas oxidationvessel to produce a preheated hydrocarbon fuel feed; second, to thefirst desulfurization vessel to produce a desulfurized hydrocarbon fuelfeed; third, to the autothermal reforming vessel to produce a firstintermediate hydrogen stream; fourth, to the second desulfurizationvessel to produce a desulfurized intermediate hydrogen stream; fifth, tothe shift vessel to produce a second intermediate hydrogen stream; andsixth, to the preferential oxidation vessel to produce the hydrogen richgas.

Turning now to the anode tail gas oxidation vessel, one illustrativeembodiment of the anode tail gas oxidation vessel includes: an oxidationcore containing a water gas shift catalyst for oxidizing fuel cell anodetail gas to produce a hot exhaust gas; and a first finned section havinga plurality of external vertical fins surrounding the oxidation core fordissipating the heat of reaction produced within the oxidation core. Thedesign of the illustrative anode tail gas oxidation vessel is such thatthe hydrocarbon fuel feed is introduced to the first finned section toproduce the preheated hydrocarbon fuel feed. In one illustrativeembodiment of the present invention, the compact fuel processor, a heatexchanger for heating water with the hot exhaust gas to produce apreheated water stream.

The illustrative compact fuel processors of the present inventionutilize a variety of heat exchanger to integrate and use the heatgenerated by certain sections to preheat feed or provide heat forendothermic reactions. In one such illustrative embodiment, theautothermal reforming vessel includes: a reforming core containing anautothermal reforming catalyst for reacting the desulfurized hydrocarbonfuel feed, the preheated water stream, and air to produce the firstintermediate hydrogen stream; and a spiral exchanger section surroundingthe reforming core. These are designed such that the spiral exchangersection contains two channels for preheating the desulfurizedhydrocarbon fuel feed with the first intermediate hydrogen stream. In asimilar manner one illustrative embodiment of the present inventionincludes a shift reactor vessel that includes a shift reactor corecontaining a water gas shift catalyst for reacting the desulfurizedintermediate hydrogen stream and water to produce the secondintermediate hydrogen stream and a second finned section having aplurality of external vertical fins surrounding the shift core fordissipating the heat of reaction produced in the shift core. The shiftreactor vessel is designed such that the desulfurized intermediatehydrogen stream is preheated in the second finned section prior to beingintroduced to the shift reactor core. It should be appreciated by one ofskill in the art that within the above illustrative embodiments, thefirst desulfurization vessel includes a desulfurization catalyst bed forsubstantially desulfurizing the preheated hydrocarbon fuel feed toproduce a desulfurized hydrocarbon fuel feed. Further it should beappreciated that the second desulfurization vessel includes adesulfurization catalyst bed for substantially desulfurizing the firstintermediate hydrogen stream to produce a desulfurized intermediatehydrogen stream. An illustrative embodiment of the preferred oxidationvessel includes a preferred oxidation catalyst bed for reacting air andthe second intermediate hydrogen stream to produce the hydrogen richgas; and a heat exchange chamber for cooling the hydrogen rich gas withwater in a cooling coil.

Alternatively the present invention includes a compact fuel processorfor converting a hydrocarbon fuel feed into hydrogen rich gas thatgenerally has a nested configuration for the reactors. In one suchillustrative embodiment, a reforming module for converting thehydrocarbon fuel feed into the hydrogen rich gas, wherein the hydrogenrich gas is suitable for direct feed to a fuel cell; and an oxidizingmodule for oxidizing fuel cell anode tail gas to produce a hot exhaustgas, wherein the hot exhaust preheats the hydrocarbon fuel feed to thereforming module. The oxidizing module of the illustrative embodimentincludes: a first heat exchanger core; an oxidation core vesselcontaining an oxidation catalyst; and a first desulfurizing vesselsurrounding the oxidation core vessel and forming a first annular spacefilled with desulfurization catalyst. This is designed such that theoxidation core vessel oxidizes the fuel cell anode tail gas to produce ahot exhaust gas; and the hydrocarbon fuel feed is preheated by the hotexhaust gas in the first heat exchanger coil to produce a preheatedhydrocarbon fuel feed. Further, the design is such that the preheatedhydrocarbon fuel feed is desulfurized in the first annular space tocreate a desulfurized hydrocarbon fuel feed. The oxidation core vesselof one preferred illustrative embodiment of the present invention has afirst set of external vertical fins for further preheating the preheatedhydrocarbon fuel feed to produce a second preheated hydrocarbon fuelfeed, and the second preheated hydrocarbon fuel feed becomes thehydrocarbon fuel feed introduced into the first annular space.

The illustrative compact fuel processor has a reforming module thatincludes: a second heat exchanger coil; a reforming core vesselcontaining an autothermal reforming catalyst bed; a second desulfurizingvessel surrounding the reforming core vessel and forming a secondannular space filled with desulfurization catalyst; a shift vesselsurrounding the second desulfurizing vessel and forming a third annularspace filled with water gas shift catalyst; and a preferred oxidationvessel surrounding the shift vessel and forming a fourth annular spacefilled with preferred oxidation catalyst. The illustrative reformingmodule is designed such that the hydrocarbon fuel feed is preheated bythe hydrogen rich gas in the second heat exchanger coil to produce athird preheated hydrocarbon fuel feed; and the third preheatedhydrocarbon fuel feed is sequentially introduced to the reforming corevessel, then to the second annular space, then to the third annularspace, and then to the fourth annular space to produce the hydrogen richgas. It is preferred that the hydrocarbon fuel feed is a desulfurizedhydrocarbon fuel feed. In one alternative illustrative embodiment thereforming core vessel has a second set of external vertical fins forfurther preheating the third preheated hydrocarbon fuel feed to producea fourth preheated hydrocarbon fuel feed. Thus, the fourth preheatedhydrocarbon fuel feed becomes the hydrocarbon fuel feed introduced tothe reforming core vessel. It should be appreciated that the thirdannular space can have a third heat exchanger coil for reactiontemperature control. Further it should be appreciated that the compactfuel processor can have an electrical heater for starting up theautothermal reforming catalyst bed.

A greater appreciation and understanding of the present invention andthe above noted illustrative embodiments can be achieved upon referenceto the following figures and accompanying descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

The description is presented with reference to the accompanying drawingsin which:

FIG. 1 depicts a simple process flow diagram for one illustrativeembodiment of the present invention.

FIG. 2 depicts a first illustrative embodiment of a compact fuelprocessor apparatus of the present invention;

FIGS. 3A and 3B depict a spiral heat exchanger combined with a reactorcore utilized in an illustrative embodiment of the present invention;and

FIG. 4 depicts a second illustrative embodiment of a compact fuelprocessor apparatus of the present invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is generally directed to an apparatus forconverting hydrocarbon fuel into a hydrogen rich gas. In a preferredaspect, the apparatus and method described herein relate to a compactprocessor for producing a hydrogen rich gas stream from a hydrocarbonfuel for use in fuel cells. However, other possible uses arecontemplated for the apparatus and method described herein, includingany use wherein a hydrogen rich stream is desired. Accordingly, whilethe invention is described herein as being used in conjunction with afuel cell, the scope of the invention is not limited to such use.

Each of the illustrative embodiments of the present invention describe afuel processor or a process for using such a fuel processor with thehydrocarbon fuel feed being directed through the fuel processor. Thehydrocarbon fuel may be liquid or gas at ambient conditions as long asit can be vaporized. As used herein the term “hydrocarbon” includesorganic compounds having C—H bonds which are capable of producinghydrogen from a partial oxidation or steam reforming reaction. Thepresence of atoms other than carbon and hydrogen in the molecularstructure of the compound is not excluded. Thus, suitable fuels for usein the method and apparatus disclosed herein include, but are notlimited to hydrocarbon fuels such as natural gas, methane, ethane,propane, butane, naphtha, gasoline, and diesel fuel, and alcohols suchas methanol, ethanol, propanol, and the like.

The fuel processor feeds include hydrocarbon fuel, oxygen, and water.The oxygen can be in the form of air, enriched air, or substantiallypure oxygen. The water can be introduced as a liquid or vapor. Thecomposition percentages of the feed components are determined by thedesired operating conditions, as discussed below.

The fuel processor effluent stream from of the present inventionincludes hydrogen and carbon dioxide and can also include some water,unconverted hydrocarbons, carbon monoxide, impurities (e.g. hydrogensulfide and ammonia) and inert components (e.g., nitrogen and argon,especially if air was a component of the feed stream).

FIG. 1 depicts a general process flow diagram illustrating the processsteps included in the illustrative embodiments of the present invention.One of skill in the art should appreciate that a certain amount ofprogressive order is needed in the flow of the reactants trough thereactors disclosed herein.

Process step A is an autothermal reforming process in which tworeactions, partial oxidation (formula I, below) and optionally alsosteam reforming (formula II, below), are combined to convert the feedstream F into a synthesis gas containing hydrogen and carbon monoxide.Formulas I and II are exemplary reaction formulas wherein methane isconsidered as the hydrocarbon:CH₄+½O₂→2H₂+CO  (I)CH₄+H₂O→3H₂+CO  (II)

The partial oxidation reaction occurs very quickly to the completeconversion of oxygen added and produces heat. The steam reformingreaction occurs slower and consumes heat. A higher concentration ofoxygen in the feed stream favors partial oxidation whereas a higherconcentration of water vapor favors steam reforming. Therefore, theratios of oxygen to hydrocarbon and water to hydrocarbon becomecharacterizing parameters. These ratios affect the operating temperatureand hydrogen yield.

The operating temperature of the autothermal reforming step can rangefrom about 550° C. to about 900° C., depending on the feed conditionsand the catalyst. The invention uses a catalyst bed of a partialoxidation catalyst with or without a steam reforming catalyst. Thecatalyst may be in any form including pellets, spheres, extrudate,monoliths, and the like. Partial oxidation catalysts should be wellknown to those with skill in the art and are often comprised of noblemetals such as platinum, palladium, rhodium, and/or ruthenium on analumina washcoat on a monolith, extrudate, pellet or other support.Non-noble metals such as nickel or cobalt have been used. Otherwashcoats such as titania, zirconia, silica, and magnesia have beencited in the literature. Many additional materials such as lanthanum,cerium, and potassium have been cited in the literature as “promoters”that improve the performance of the partial oxidation catalyst.

Steam reforming catalysts should be known to those with skill in the artand can include nickel with amounts of cobalt or a noble metal such asplatinum, palladium, rhodium, ruthenium, and/or iridium. The catalystcan be supported, for example, on magnesia, alumina, silica, zirconia,or magnesium aluminate, singly or in combination. Alternatively, thesteam reforming catalyst can include nickel, preferably supported onmagnesia, alumina, silica, zirconia, or magnesium aluminate, singly orin combination, promoted by an alkali metal such as potassium.

Process step B is a cooling step for cooling the synthesis gas streamfrom process step A to a temperature of from about 200° C. to about 600°C., preferably from about 300° C. to about 500° C., and more preferablyfrom about 375° C. to about 425° C., to optimize the temperature of thesynthesis gas effluent for the next step. This cooling may be achievedwith heat sinks, heat pipes or heat exchangers depending upon the designspecifications and the need to recover/recycle the heat content of thegas stream. The heat exchanger can be of any suitable construction knownto those with skill in the art including shell and tube, plate, spiral,etc. Alternatively, or in addition thereto, cooling step B may beaccomplished by injecting additional feed components such as fuel, airor water. Water is preferred because of its ability to absorb a largeamount of heat as it is vaporized to steam. The amounts of addedcomponents depend upon the degree of cooling desired and are readilydetermined by those with skill in the art.

Process step C is a purifying step. One of the main impurities of thehydrocarbon stream is sulfur, which is converted by the autothermalreforming step A to hydrogen sulfide. The processing core used inprocess step C preferably includes zinc oxide and/or other materialcapable of absorbing and converting hydrogen sulfide, and may include asupport (e.g., monolith, extrudate, pellet etc.). Desulfurization isaccomplished by converting the hydrogen sulfide to water in accordancewith the following reaction formula III:H₂S+ZnO→H₂O+ZnS  (III)

Other impurities such as chlorides can also be removed. The reaction ispreferably carried out at a temperature of from about 300° C. to about500° C., and more preferably from about 375° C. to about 425° C. Zincoxide is an effective hydrogen sulfide absorbent over a wide range oftemperatures from about 25° C. to about 700° C. and affords greatflexibility for optimizing the sequence of processing steps byappropriate selection of operating temperature.

The effluent stream may then be sent to a mixing step D in which wateris optionally added to the gas stream. The addition of water lowers thetemperature of the reactant stream as it vaporizes and supplies morewater for the water gas shift reaction of process step E (discussedbelow). The water vapor and other effluent stream components are mixedby being passed through a processing core of inert materials such asceramic beads or other similar materials that effectively mix and/orassist in the vaporization of the water. Alternatively, any additionalwater can be introduced with feed, and the mixing step can berepositioned to provide better mixing of the oxidant gas in the COoxidation step G disclosed below.

Process step E is a water gas shift reaction that converts carbonmonoxide to carbon dioxide in accordance with formula IV:H₂O+CO→H₂+CO₂  (IV)

This is an important step because carbon monoxide, in addition to beinghighly toxic to humans, is a poison to fuel cells. The concentration ofcarbon monoxide should preferably be lowered to a level that can betolerated by fuel cells, typically below 50 ppm. Generally, the watergas shift reaction can take place at temperatures of from 150° C. to600° C. depending on the catalyst used. Under such conditions, most ofthe carbon monoxide in the gas stream is converted in this step.

Low temperature shift catalysts operate at a range of from about 150° C.to about 300° C. and include for example, copper oxide, or coppersupported on other transition metal oxides such as zirconia, zincsupported on transition metal oxides or refractory supports such assilica, alumina, zirconia, etc., or a noble metal such as platinum,rhenium, palladium, rhodium or gold on a suitable support such assilica, alumina, zirconia, and the like.

High temperature shift catalysts are preferably operated at temperaturesranging from about 300° to about 600° C. and can include transitionmetal oxides such as ferric oxide or chromic oxide, and optionallyincluding a promoter such as copper or iron silicide. Also included, ashigh temperature shift catalysts are supported noble metals such assupported platinum, palladium and/or other platinum group members.

The processing core utilized to carry out this step can include a packedbed of high temperature or low temperature shift catalyst such asdescribed above, or a combination of both high temperature and lowtemperature shift catalysts. The process should be operated at anytemperature suitable for the water gas shift reaction, preferably at atemperature of from 150° C. to about 400° C. depending on the type ofcatalyst used. Optionally, a cooling element such as a cooling coil maybe disposed in the processing core of the shift reactor to lower thereaction temperature within the packed bed of catalyst. Lowertemperatures favor the conversion of carbon monoxide to carbon dioxide.Also, a purification processing step C can be performed between high andlow shift conversions by providing separate steps for high temperatureand low temperature shift with a desulfurization module between the highand low temperature shift steps.

Process step F is a cooling step performed in one embodiment by a heatexchanger. The heat exchanger can be of any suitable constructionincluding shell and tube, plate, spiral, etc. Alternatively a heat pipeor other form of heat sink may be utilized. The goal of the heatexchanger is to reduce the temperature of the gas stream to produce aneffluent having a temperature preferably in the range of from about 90°C. to about 150° C.

Oxygen is added to the process in step F. The oxygen is consumed by thereactions of process step G described below. The oxygen can be in theform of air, enriched air, or substantially pure oxygen. The heatexchanger may by design provide mixing of the air with the hydrogen richgas. Alternatively, the embodiment of process step D may be used toperform the mixing.

Process step G is an oxidation step wherein almost all of the remainingcarbon monoxide in the effluent stream is converted to carbon dioxide.The processing is carried out in the presence of a catalyst for theoxidation of carbon monoxide and may be in any suitable form, such aspellets, spheres, monolith, etc. Oxidation catalysts for carbon monoxideare known and typically include noble metals (e.g., platinum, palladium)and/or transition metals (e.g., iron, chromium, manganese), and/orcompounds of noble or transition metals, particularly oxides. Apreferred oxidation catalyst is platinum on an alumina washcoat. Thewashcoat may be applied to a monolith, extrudate, pellet or othersupport. Additional materials such as cerium or lanthanum may be addedto improve performance. Many other formulations have been cited in theliterature with some practitioners claiming superior performance fromrhodium or alumina catalysts. Ruthenium, palladium, gold, and othermaterials have been cited in the literature as being active for thisuse.

Two reactions occur in process step G: the desired oxidation of carbonmonoxide (formula V) and the undesired oxidation of hydrogen (formulaVI) as follows:CO+½O₂→CO₂  (V)H₂+½O₂→H₂O  (VI)

The preferential oxidation of carbon monoxide is favored by lowtemperatures. Since both reactions produce heat it may be advantageousto optionally include a cooling element such as a cooling coil disposedwithin the process. The operating temperature of process is preferablykept in the range of from about 90° C. to about 150° C. Process step Gpreferably reduces the carbon monoxide level to less than 50 ppm, whichis a suitable level for use in fuel cells, but one of skill in the artshould appreciate that the present invention can be adapted to produce ahydrogen rich product with of higher and lower levels of carbonmonoxide.

The effluent exiting the fuel processor is a hydrogen rich gascontaining carbon dioxide and other constituents which may be presentsuch as water, inert components (e.g., nitrogen, argon), residualhydrocarbon, etc. Product gas may be used as the feed for a fuel cell orfor other applications where a hydrogen rich feed stream is desired.Optionally, product gas may be sent on to further processing, forexample, to remove the carbon dioxide, water or other components.

In one illustrative embodiment of the present invention, the fuelprocessor is of modular construction having dual reactor stacks whichinclude a reforming stack and a purification stack. Each stack iscomposed of individual modular units, which are separable,rearrangeable, and individually replaceable. The modular units may beused in any orientation, e.g., vertical or horizontal orientation. Theillustrated combination of dual reactor stacks is adapted to be used inconjunction with a fuel cell such that the hydrogen rich product gas ofthe reactor described herein is supplied directly to a fuel cell as afeed stream. While the modules can have any cross sectionalconfiguration, such as circular, rectangular, triangular, etc., acircular cross section is preferred resulting in the reactor stackshaving a generally tubular shape.

The modules can be fabricated from any material capable of withstandingthe operating conditions and chemical environment of the reactionsdescribed herein and can include, for example, stainless steel, Inconel,Incoloy, Hastelloy, and the like. The reaction pressure is preferablefrom about 0 to about 100 psig, although higher pressures may beemployed. The operating pressure of the fuel processor depends upon thedelivery pressure required by the fuel cell. For fuel cells operating inthe 1 to 20 kW range an operating pressure of 0 to about 100 psig isgenerally sufficient. The modules are of such dimensions so as to safelycontain the reaction at the desired operating pressures andtemperatures.

Turning now to FIG. 2, a dual stack fuel processor is shown including areforming stack 10 and a purification stack 20. Fuel 100 is preheated bythe vertical finned heat exchanger that serves as the heat sink for theanode tail gas oxidizer 104. The anode tail gas oxidizer oxidizes theunused gas from the anode of the fuel cell (not shown) using catalyticcombustion. The heat generated is transferred by the vertical finnedheat exchanger 102 to the fuel to preheat the fuel. The exhaust from theanode tail gas oxidizer 108 is sent to a second heat exchanger where anyremaining heat is transferred to a water stream 124. The preheated fuel114 is directed to a first desulfurization reactor 116, in which sulfurcompounds present in the fuel are removed catalytically. Thedesulfurized fuel 118 is then routed to the start-up heater. Thestart-up heater plays two roles, first to provide a mixing point for thefuel 118, air 122 and water 124 that are needed for the auto-thermalreforming reactor 128. Secondly, the startup heater can be used duringstart-up to provide the additional heat to the fuel/air/water mixtureneeded to initiate the auto-thermal reformation reaction. Theauto-thermal reformation reactor is composed of a spiral heat exchangerthat simultaneously preheats the fuel/air/water mixture and cools theresulting product gas which is mostly a mixture of hydrogen, carbonmonoxide, carbon dioxide and nitrogen gases. Such a spiral heatexchanger is described in greater detail in co-pending applicationentitled: “Reactor Module for Use in a Compact Fuel Processor” filed onDec. 5, 2001, the contents of which are hereby incorporated byreference.

A specific illustrative example of such a heat exchanger is shown inFIGS. 3A and 3B. Such and illustrative reactor module comprises a spiralheat exchanger with a fixed bed reactor located in the core of thespiral heat exchanger. In order to maximize heat transfer in a typicalspiral heat exchanger design, hot fluid is introduced into the core ofthe unit and spirals outward toward the outside channel, while the coldfluid enters the unit at the outside channel and spirals towards thecore. Countercurrent flow is usually employed between the hot and coldchannels in a spiral exchanger to maximize heat transfer. The presentinvention takes advantage of this type of heat exchange to preheat areactor feed with the hot reactor effluent produced by a reactor bedlocated at the core of the spiral exchanger. This design results inlower pressure drops, higher energy efficiency, short flow paths, andcreates a compact modular design consistent with a compact fuelprocessor.

FIG. 3A illustrates an overhead cross-sectional view of one illustrativeembodiment of such a reactor module. FIG. 3B illustrates a sidecross-sectional view of one illustrative embodiment of such a reactormodule. Reactor module 400 consists essentially of a spiral exchangerwith a fixed bed reactor 410 located in the core of the spiralexchanger. The spiral heat exchanger portion of the module is composedof two long, flat plates wrapped around the reactor core, creating twoconcentric spiral channels—an inlet spiral passage 430 and an outletspiral passage 440. The channels are seal-welded on alternate sides toprovide a sturdy barrier between the fluids. A cover is fitted on eachside, and a full-faced gasket is positioned between each cover andspiral element to prevent leaks.

Module feed MF enters reactor module 400 at module inlet nozzle 420, isintroduced into inlet spiral passage 430, and proceeds through inletspiral passage 430 to reactor inlet piping 450. A flow distributionmanifold 460 is utilized to evenly distribute flow into reactor 410.Reactor 410 is an autothermal reforming reactor as in process step A ofFIG. 1. The reactor may be a fixed bed reactor containing supportedcatalyst particles or the reactor bed may be a monolith with catalyticmaterial coated on to the surface of the structural members, the choiceof catalyst being a design decision consistent with the considerationsdiscussed previously regarding the process steps of FIG. 1.

A flow collection manifold 470 is utilized to direct the hot reactorproduct to the reactor outlet piping 480. From there, the hot productgases proceed through the outlet spiral passage, and ultimately thecooled module effluent ME is produced from the module outlet nozzle 490.Such an apparatus as described herein can be designed by one skilled inthe art to effectively and efficiently preheat the module feed MF to theappropriate reaction temperature before entering the reactor whilecooling the hot reaction product to an appropriate temperature forfurther processing in the fuel processor. Module 400 in thisillustrative embodiment shows the spiraling relationship between theinlet spiral passage 430 and the outlet spiral passage 440, but one ofskill in the art should appreciate that the extent of spiraling utilizedin the present invention is a design consideration unique to thereaction and operating conditions of each specific module.

The cooled product gas of the auto-thermal reformation reactor 130 isthen returned to the purification stack in which a desulfurzationreaction is carried out in the second desulfurization reactor 132. Thedesulfurized gas 134 is then provided to the water gas shift reactor136. The water gas shift reactor, like the anode tail gas oxidizerreactor, utilizes vertical finned heat exchangers 138 to regulate thetemperature of the reaction. Heat is absorbed by water stream 124. Theproduct gas of the shift reactor is combined with air or anothersuitable oxygen source 142 and the mixture is fed to the preferentialoxidation reactor 144. The preferential oxidation reactor 144substantially removes traces of carbon monoxide that may be present byuse of a selective oxidation catalyst. A heat exchanger 146 controls thetemperature of the partial oxidation reactor and preheats water 148 aportion of which is used as feed to the auto-thermal reformationreactor. Suitably pure hydrogen gas 150 is produced from thepreferential oxidation reactor 144. The hydrogen containing gas ispreferably used in a fuel cell or may be stored or used in otherprocesses.

One of skill in the art after reviewing the above description shouldunderstand and appreciate that each module performs a separateoperational function and is generally configured as shown in FIG. 2.Feed stream F (100) is introduced through inlet pipe (not shown) andproduct gas P (150) is drawn off via outlet pipe (not shown). Module 128is the autothermal reforming module corresponding to process step A ofFIG. 1. The autothermal reforming module has built into is a spiral heatexchanger the simultaneously heats the incoming fuel mixture and coolsthe outgoing product gas which corresponds to process step B of FIG. 1.Module 132 is a purifying module corresponding to process step C ofFIG. 1. Module 136 is a water gas shift module corresponding to processstep E of FIG. 1. The cooling step corresponding to process step F ofFIG. 1 is carried out by vertical finned heat exchanger 138. In thisillustrative embodiment, heat exchanger 138 is shown as a general heatsink for Module 136. Module 144 is an oxidation step corresponding toprocess step G of FIG. 1. Air source 142 provides a source for oxygen toprocess gas for the oxidation reaction (Equation V) of Module 144.Module 144 also contains a heat exchanger 146 (partially shown)positioned within or surrounding the catalyst bed so as to maintain adesired oxidation reaction temperature. One of skill in the art shouldappreciate that the process configuration described in this embodimentmay vary depending on numerous factors, including but not limited tofeedstock quality and required product quality.

Turning now to FIG. 4, an alternative illustrative embodiment of a dualstack fuel processor is shown in which there is a reforming stack 30 anda oxidizing stack 40. As will become apparent below, the reforming stack30 generally carries out the reformation process in which fuel isconverted into suitably pure hydrogen gas for use with a fuel cell (notshown). The oxidation stack generally serves as a means for recoveringthe heat content of the anode tail gas generated by the fuel cell andpreheats the fuel for the reforming stack.

Fuel 200 is provided to the reforming stack 40 that includes two majorcomponents, the anode tail gas oxidation reactor 204 and thedesulfurization reaction 210. The anode tail gas oxidation reactor isdesigned such that it catalytically oxidizes the anode tail gas 206generated from a fuel cell. The heat generated is transferred to thefuel 200 by vertical fin heat exchangers 202 generating a cooled exhaust208. The heated fuel is then subjected to a desulfurization reactor 210that substantially removes the sulfur compounds present in the fuel. Thedesulfurized fuel 212 is provided to the reforming stack 30 and combinedwith air 214 and hot water/steam 216. This mixture of fuel/air/waterpasses through a distribution manifold 218 which directs the mixturethrough a vertical fin heat exchanger 220. The pre heated fuel/air/watermixture is then introduced into the auto-thermal reformation reactor224. During start-up, an electrical pre-heater element 222 is installedat the bottom of the auto-thermal reformation reactor. However, oncestarted the heat generated by the auto-thermal reformation reactor issufficient to heat the fuel/air/water mixture via the vertical finnedheat exchangers 220. The product gas from the auto-thermal reformingreactor is directed to a second desulfurization reactor 226 whichremoves any remaining sulfur compounds from the gas product stream. Thedesulfurized gas is then introduced into the water-gas shift reactor228. The temperature of the shift reactor is controlled by tube heatexchangers 232. It should be noted at this point that the heat exchangerin the present illustrative embodiment is designed as one continuoustube routed throughout the reforming stack. Points A and B arerespectively connected to each other such that the flow of water throughthe tube is continuous. After passing through the shift reactor, air 229is mixed with the hydrogen containing gas and passed to a preferentialoxidation reactor 230. In the preferential oxidation reactor traceamounts of carbon monoxide are removed so as to purify the hydrogencontaining gas for use in a fuel cell. The product gas if further cooledby heat exchanger coils 232 and leaves the reforming stack as hydrogencontaining gas 236. The hydrogen containing gas is preferably used in afuel cell or may be stored or used in other processes.

One of skill in the art after reviewing the above description shouldunderstand and appreciate that each module performs a separateoperational function. Feed stream F (200) is introduced through inletpipe (not shown) and product gas P (236) is drawn off via outlet pipe(not shown). Module 224 is the autothermal reforming modulecorresponding to process step A of FIG. 1. The autothermal reformingmodule has built into it a vertical fin heat exchanger thesimultaneously heats the incoming fuel mixture and cools the outgoingproduct gas which corresponds to process step B of FIG. 1. An electricheater 222, is installed at the bottom inlet of the autothermalreformation reactor for start-up heat. Module 226 is a purifying modulecorresponding to process step C of FIG. 1. Module 228 is a water gasshift module corresponding to process step E of FIG. 1. The cooling stepcorresponding to process step F of FIG. 1 is carried out by finned tubeheat exchanger 232. In this illustrative embodiment, heat exchanger 232is shown as a general heat sink for the entire reforming stack, however,one of skill in the art could redesign the heat exchangers to havemultiple flows and heat exchangers. Module 230 is an oxidation stepcorresponding to process step G of FIG. 1. Air source 229 provides asource for oxygen to process gas for the oxidation reaction (Equation V)of Module 230. Module 230 also contains a heat exchanger 232 (partiallyshown) positioned within or surrounding the catalyst bed so as tomaintain a desired oxidation reaction temperature. One of skill in theart should appreciate that the process configuration described in thisembodiment may vary depending on numerous factors, including but notlimited to feedstock quality and required product quality.

Upon review of the above disclosure one of ordinary skill in the artshould understand and appreciate that one illustrative embodiment of thepresent invention is a compact fuel processor for converting ahydrocarbon fuel feed into a purified hydrogen rich gas. Such anillustrative embodiment includes a reforming stack for converting thehydrocarbon fuel feed into a hydrogen rich gas; and a purification stackfor producing the hydrogen rich gas suitable for direct feed to a fuelcell. In one preferred illustrative embodiment, the reforming stackincludes a first plurality of cylindrical vessels, in which the firstplurality of cylindrical vessels are stackable without the need forconnecting piping between each vessel. Further, the purification stackincludes a second plurality of cylindrical vessels, in which theplurality of cylindrical vessels are stackable without the need forconnecting piping between each vessel. One illustrative embodiment hasthe reforming stack is aligned vertically.

The reforming stack of one illustrative embodiment includes a shiftvessel, an autothermal reforming vessel, and an anode tail gas oxidationvessel. The purification stack of the illustrative embodiment includesan oxidation vessel, a first desulfurization vessel, and a seconddesulfurization vessel.

In the present illustrative embodiment, the hydrocarbon fuel feed issequentially introduced first, to the anode tail gas oxidation vessel toproduce a preheated hydrocarbon fuel feed; second, to the firstdesulfurization vessel to produce a desulfurized hydrocarbon fuel feed;third, to the autothermal reforming vessel to produce a firstintermediate hydrogen stream; fourth, to the second desulfurizationvessel to produce a desulfurized intermediate hydrogen stream; fifth, tothe shift vessel to produce a second intermediate hydrogen stream; andsixth, to the preferential oxidation vessel to produce the hydrogen richgas. Turning now to the anode tail gas oxidation vessel, oneillustrative embodiment of the anode tail gas oxidation vessel includes:an oxidation core containing a water gas shift catalyst for oxidizingfuel cell anode tail gas to produce a hot exhaust gas; and a firstfinned section having a plurality of external vertical fins surroundingthe oxidation core for dissipating the heat of reaction produced withinthe oxidation core. The design of the illustrative anode tail gasoxidation vessel is such that the hydrocarbon fuel feed is introduced tothe first finned section to produce the preheated hydrocarbon fuel feed.In one illustrative embodiment of the present invention, the compactfuel processor, a heat exchanger for heating water with the hot exhaustgas to produce a preheated water stream.

The illustrative compact fuel processors of the present inventionutilize a variety of heat exchanges to integrate and use the heatgenerated by certain section to preheat feed or provide heat forendothermic reactions. In one such illustrative embodiment, theautothermal reforming vessel includes: a reforming core containing anautothermal reforming catalyst for reacting the desulfurized hydrocarbonfuel feed, the preheated water stream, and air to produce the firstintermediate hydrogen stream; and a spiral exchanger section surroundingthe reforming core. These are designed such that the spiral exchangersection contains two channels for preheating the desulfurizedhydrocarbon fuel feed with the first intermediate hydrogen stream. In asimilar manner one illustrative embodiment of the present inventionincludes a shift reactor vessel that includes a shift reactor corecontaining a water gas shift catalyst for reacting the desulfurizedintermediate hydrogen stream and water to produce the secondintermediate hydrogen stream and a second finned section having aplurality of external vertical fins surrounding the shift core fordissipating the heat of reaction produced in the shift core. The shiftreactor vessel is designed such that the desulfurized intermediatehydrogen stream is preheated in the second finned section prior to beingintroduced to the shift reactor core. It should be appreciated by one ofskill in the art that within the above illustrative embodiments, thefirst desulfurization vessel includes a desulfurization catalyst bed forsubstantially desulfurizing the preheated hydrocarbon fuel feed toproduce a desulfurized hydrocarbon fuel feed. Further it should beappreciated that the second desulfurization vessel includes adesulfurization catalyst bed for substantially desulfurizing the firstintermediate hydrogen stream to produce a desulfurized intermediatehydrogen stream. An illustrative embodiment of the preferred oxidationvessel includes a preferred oxidation catalyst bed for reacting air andthe second intermediate hydrogen stream to produce the hydrogen richgas; and a heat exchange chamber for cooling the hydrogen rich gas withwater in a cooling coil.

One of ordinary skill in the art, upon review of the present disclosure,should also appreciate that another illustrative embodiment of thepresent invention includes a compact fuel processor for converting ahydrocarbon fuel feed into hydrogen rich gas that generally has a radialflow through the reactor. In one such illustrative embodiment, areforming module for converting the hydrocarbon fuel feed into thehydrogen rich gas, wherein the hydrogen rich gas is suitable for directfeed to a fuel cell; and an oxidizing module for oxidizing fuel cellanode tail gas to produce a hot exhaust gas, wherein the hot exhaustpreheats the hydrocarbon fuel feed to the reforming module.

The oxidizing module of the illustrative embodiment includes: a firstheat exchanger core; an oxidation core vessel containing an oxidationcatalyst; and a first desulfurizing vessel surrounding the oxidationcore vessel and forming a first annular space filled withdesulfurization catalyst.

This is designed such that the oxidation core vessel oxidizes the fuelcell anode tail gas to produce a hot exhaust gas; and the hydrocarbonfuel feed is preheated by the hot exhaust gas in the first heatexchanger coil to produce a preheated hydrocarbon fuel feed. Further,the design is such that the preheated hydrocarbon fuel feed isdesulfurized in the first annular space to create a desulfurizedhydrocarbon fuel feed. The oxidation core vessel of one preferredillustrative embodiment of the present invention has a first set ofexternal vertical fins for further preheating the preheated hydrocarbonfuel feed to produce a second preheated hydrocarbon fuel feed, and thesecond preheated hydrocarbon fuel feed becomes the hydrocarbon fuel feedintroduced into the first annular space.

The illustrative compact fuel processor has a reforming module thatincludes: a second heat exchanger coil; a reforming core vesselcontaining an autothermal reforming catalyst bed; a second desulfurizingvessel surrounding the reforming core vessel and forming a secondannular space filled with desulfurization catalyst; a shift vesselsurrounding the second desulfurizing vessel and forming a third annularspace filled with water gas shift catalyst; and a preferred oxidationvessel surrounding the shift vessel and forming a fourth annular spacefilled with preferred oxidation catalyst. The illustrative reformingmodule is designed such that the hydrocarbon fuel feed is preheated bythe hydrogen rich gas in the second heat exchanger coil to produce athird preheated hydrocarbon fuel feed; and the third preheatedhydrocarbon fuel feed is sequentially introduced to the reforming corevessel, then to the second annular space, then to the third annularspace, and then to the fourth annular space to produce the hydrogen richgas. It is preferred that the hydrocarbon fuel feed is a desulfurizedhydrocarbon fuel feed. In one alternative illustrative embodiment thereforming core vessel has a second set of external vertical fins forfurther preheating the third preheated hydrocarbon fuel feed to producea fourth preheated hydrocarbon fuel feed. Thus, the fourth preheatedhydrocarbon fuel feed becomes the hydrocarbon fuel feed introduced tothe reforming core vessel. It should be appreciated that the thirdannular space can have a third heat exchanger coil for reactiontemperature control. Further it should be appreciated that the compactfuel processor can have an electrical heater for starting up theautothermal reforming catalyst bed.

Yet another illustrative embodiment of the present invention is acompact fuel processor for converting a hydrocarbon fuel feed intohydrogen rich gas, that includes a heat exchanger coil; a reforming corevessel containing an autothermal reforming catalyst bed; a desulfurizingvessel surrounding the reforming core vessel and forming a first annularspace filled with desulfurization catalyst; a shift vessel surroundingthe desulfurizing vessel and forming a second annular space filled withwater gas shift catalyst; and a preferred oxidation vessel surroundingthe shift vessel and forming a third annular space filled with preferredoxidation catalyst. Such an illustrative compact fuel processor isdesigned such that the hydrocarbon fuel feed is preheated by thehydrogen rich gas in the heat exchanger coil to produce a preheatedhydrocarbon fuel feed; and the preheated hydrocarbon fuel feed issequentially introduced to the reforming core vessel, then to the secondannular space, then to the third annular space, and then to the fourthannular space to produce the hydrogen rich gas.

It is preferred within this illustrative embodiment that the reformingcore vessel has a set of external vertical fins for further preheatingthe preheated hydrocarbon fuel feed to produce a second preheatedhydrocarbon fuel feed. Thus, the second preheated hydrocarbon fuel feedbecomes the preheated hydrocarbon fuel feed introduced to the reformingcore vessel. It should also be noted that the second annular space mayhave a second heat exchanger coil for reaction temperature control.Further the present illustrative embodiment can include an electricalheater for starting up the autothermal reforming catalyst bed.

While the apparatus, compositions and methods of this invention havebeen described in terms of preferred or illustrative embodiments, itwill be apparent to those of skill in the art that variations may beapplied to the process described herein without departing from theconcept and scope of the invention. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the scope and concept of the invention as it is set out in thefollowing claims.

1. A compact fuel processor for converting a hydrocarbon fuel feed intoa purified hydrogen rich gas, comprising: a reforming stack forconverting the hydrocarbon fuel feed into a hydrogen rich gas, whereinthe reforming stack includes a first plurality of cylindrical vessels,each of said first plurality of cylindrical vessels is stackable withoutthe need for connecting piping between each vessel; and a purificationstack for producing the hydrogen rich gas suitable for direct feed to afuel cell.
 2. The compact fuel processor of claim 1, wherein thepurification stack includes a second plurality of cylindrical vessels,wherein the plurality of cylindrical vessels are stackable without theneed for connecting piping between each vessel.
 3. The compact fuelprocessor of claim 2, wherein the reforming stack is aligned vertically.4. The compact fuel processor of claim 1, wherein the reforming stackcomprises a shift vessel, an autothermal reforming vessel, and an anodetail gas oxidation vessel; and wherein the purification stack comprisesa preferred oxidation vessel, a first desulfurization vessel, and asecond desulfurization vessel.
 5. The compact fuel processor of claim 4,wherein the hydrocarbon fuel feed is sequentially introduced to: first,to the anode tail gas oxidation vessel to produce a preheatedhydrocarbon fuel feed; second, to the first desulfurization vessel toproduce a desulfurized hydrocarbon fuel feed; third, to the autothermalreforming vessel to produce a first intermediate hydrogen stream;fourth, to the second desulfurization vessel to produce a desulfurizedintermediate hydrogen stream; fifth, to the shift vessel to produce asecond intermediate hydrogen stream; and sixth, to the preferentialoxidation vessel to produce the hydrogen rich gas.
 6. The compact fuelprocessor of claim 5, wherein the anode tail gas oxidation vesselcomprises: an oxidation core containing a water gas shift catalyst foroxidizing fuel cell anode tail gas to produce a hot exhaust gas; and afirst finned section having a plurality of external vertical finssurrounding the oxidation core for dissipating the heat of reactionproduced within the oxidation core; wherein the hydrocarbon fuel feed isintroduced to the first finned section to produce the preheatedhydrocarbon fuel feed.
 7. The compact fuel processor of claim 6, furthercomprising a heat exchanger for heating water with the hot exhaust gasto produce a preheated water stream.
 8. The compact fuel processor ofclaim 5, wherein the autothermal reforming vessel comprises: a reformingcore containing an autothermal reforming catalyst for reacting thedesulfurized hydrocarbon fuel feed, the preheated water stream, and airto produce the first intermediate hydrogen stream; and a spiralexchanger section surrounding the reforming core; wherein the spiralexchanger section contains two channels for preheating the desulfurizedhydrocarbon fuel feed with the first intermediate hydrogen stream. 9.The compact fuel processor of claim 5, wherein the shift reactor vesselcomprises: a shift core containing a water gas shift catalyst forreacting the desulfurized intermediate hydrogen stream and water toproduce the second intermediate hydrogen stream; and a second finnedsection having a plurality of external vertical fins surrounding theshift core for dissipating the heat of reaction produced in the shiftcore; wherein the desulfurized intermediate hydrogen stream is preheatedin the second finned section prior to being introduced to the shiftcore.
 10. The compact fuel processor of claim 5, wherein the firstdesulfurization vessel comprises a desulfurization catalyst bed forsubstantially desulfurizing the preheated hydrocarbon fuel feed toproduce a desulfurized hydrocarbon fuel feed.
 11. The compact fuelprocessor of claim 5, wherein the second desulfurization vesselcomprises a desulfurization catalyst bed for substantially desulfurizingthe first intermediate hydrogen stream to produce a desulfurizedintermediate hydrogen stream.
 12. The compact fuel processor of claim 5,wherein the preferred oxidation vessel comprises: a preferred oxidationcatalyst bed for reacting air and the second intermediate hydrogenstream to produce the hydrogen rich gas; and a heat exchange chamber forcooling the hydrogen rich gas with water in a cooling coil.